Solid State Image Sensors within the prior art typically are placed within a package having a glass or plastic cover on the package to allow incident light to strike the surface of the imager. The cover is typically sealed to the sensor package using an epoxy that has been either silk-screened or dispensed onto the cover. A more common technique is to place a thin line of epoxy beads around the outer edge of a sensor package as seen in FIG. 1 to attach the cover glass. There is a basic problem in the arrangement shown in FIG. 1. The inside surface of the cover glass allows light entering the package cavity to be reflected from the surfaces inside the package cavity, such as bond wires, lead frame, etc., and back to the inside surface of the cover. These reflections can subsequently be directed back to the imager causing undesired information to be sensed as part of the incident image.
These undesired reflections have been successfully reduced by the use of a separate light shield, typically of some blackened metallic material, mounted into the package cavity, above the imager and below the cover, prior to sealing the cover onto the package, as shown in FIG. 2. The aperture opening in this light shield is typically slightly larger than the imager active region so as not to impede the incoming light over the sensor, but successfully masks internal light reflections. The disadvantage to this configuration is the additional labor cost associated with the addition of the separate light shield containing the aperture, as well as the cost of the additional component.
From the foregoing discussion, it should be apparent that there remains a need in the art for a more economically advantageous manner of placing light shields on image sensing elements.